Apparatus for automatic film testing

ABSTRACT

Apparatus for automatic sensitometric testing of photographic film, characterized by direct sequence of stages, synchronized one with another with respect to the feed rate of a test film strip to be passed therethrough: (a) a sensitometer in which the test film strip is passed in synchronism with a density wedge at constant speed past an exposure slit; (b) a developing and fixing bath with washing and drying sections; and (c) a densitometer, the test film strip being passed at constant speed or at a rate controlled by the densitometer itself past a photoelectric data indicator while a scanner is connected after densitometer. The device permits rapid access to sensitometric data in a few minutes.

O Unlted States Patent 1151- 3,636,851 Furst 1 Jan. 25, 1972 [54]APPARATUS FOR AUTOMATIC FILM 3,244,062 4/1966 Sweet ..356/203 {TESTIN3,377,467 4/1968 Staunton et a1. v G 3,413,065 11/1968 Funk [72]Inventor: Karl-Heinz Fiirst, Gotzenhain, Germany 3,440,935 1969 Sanford3,462,221 8/1969 Tajima et al... [73] a}; "P P 3,471,242 10/1969 Nichols....356/202 3,525,869 8/1970 Gubisch ..356/201 x [22] Filed: Oct. 8,1969 Primary Examiner-John M. Horan [2]] Appl' 8 Assistant Examiner-AlanMathews Attorney-Lynn Barratt Morris [30] Forei n A lication Prio it Dta 8 pp y 57 ABSTRACT Nov. 7, 1968 Germany ..P 18 07 403.8

Apparatus for automatlc sens1tometric testmg of photographic 52 us. c1...95/89 11, 95/94 R 356/202 haramized by direct sequence stages,syhchmnized 51 1m. 01. ..cosa a/os whh anmh" with the feed a test mm 581Field of Search 1.95/89, 905,94, 1; 356/201 Strip he Passed hemhmugh (a)a sehsimmeter which 356/202 the test film strip is passed in synchronismwith a density wedge at constant speed past an exposure slit; (b) adevelop- 5 Rehrences Cited ing and fixing bath with washing and dryingsections; and (c) a densitometer, the test film strip being passed atconstant speed UNITED STATES PATENTS or at a rate controlled by thedensitometer itself past a photoelectric data indicator while a scanneris connected after lrjlunt dehsiometer. The device permits rapid accessto sensitomet 2'762278 9/1956 ati 3 ric data in a few minutes. 3,090,2905/1963 Ross ..95/89 8 Clainis, 3 Drawing Figures PATENTEU M25182 SHEET 1UF 3 INVENTOR Korl- Heinz First BY 25 M 73M W ATTORNEY PATENTED JANZS19. 2

SHEET 2 [IF 3 FIG.

AFI

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ATTORNEY PATENTEU JAN25 57? I sum 3 or 3 ATTORNEY APPARATUS FORAUTOMATIC FILM TESTING sensitometric testing of samples takes somuchtime that the results of such sensitometric testing cannot be usedto guide the production operations.

Therefore, it is the object of the invention to provide an apparatus forautomatic sensitometric testing with which the results of thesensitometric testing become available in a very short time, so that, ifnecessary, interventionin the control of production operations can beundertaken. Beyondthis, aswas customary previously, the apparatus alsoshould-give records of the test results on the production batchconcerned that are available at any later time.

The problem posed is solved by the invention through the directsuccession of the following stations, which are correlated with respectto the transport velocity of a filmstrip passed through for testing:

A. A sensitometer, in which the filmstrips to be tested are led insynchronism with a density wedge at a constant speed past an exposureslit,

B. a developing and fixing bathwith washing and drying sections orunits, and

C. a densitometer, in which the filmstrips to be tested are led at aconstant speed past a photoelectric measurement transmitter; in doingwhich an evaluation apparatus is provided beyond the densitometer.

The apparatus of the invention makes it possible for all importantsensitometric data to be available in a few minutes, at

most 3 to 5 minutes, after introduction-of the unexposedfilm to betested. Through this substantial shortening of the time necessary forthe sensitometric testing, it is possible to intervene in a processoperation promptly.

In a preferred embodiment of the invention the densitometer isconstructed as a digital densitometer with linearizing arrangements. Inthis way the sensitometric data determined are available immediately indigital representation, so that the evaluation of these data issimplified substantially and is possible much faster. Through thedigital representation of the sensitometric data determined, there is apossibility of attaching a process computer to the digital densitometerfor guiding and controlling the manufacturing operation. Then thedensitometric data in digital representation are introduced in theprocess computer along with additional measured data to control andguide the entire manufacturing operation.

Within the scope of the invention it is especially suitable to combinethe developing and fixing baths and the washing and drying sections intoa composite rolLdeveloping machine.

For filmstrips coated on both sides, it is possible within the scope ofthe invention, to provide a two-armed light conductor in thesensitometer for splitting the light beam and exposing both coatedsurfaces of the filmstrips.

In the following, examples of embodiments of the invention are explainedin detail with reference to the drawings. They include:

FIG. 1, a schematic block representation of one embodiment of theapparatus of the invention;

FIG. 2, a schematic diagram of a prospective digital densitometer withinthe scope of the invention and FIG. 3, a schematic diagram of a seconddigital densitometer that can be used within the scope of the invention.

In the example of FIG. I, the apparatus of the invention, in essence,contains three units in direct succession, that are correlated withrespect to the transport velocity of a filmstrip 1 to be passed throughfor testing that includes a sensitometer A, adeveloping-fixing-washing-drying unit B and a densitometer C Thefilmstrip l is introduced in the sensitometer A and there is grasped bythe transport rollers 2. These transport rollers 2 lead the filmstrip lat a constant speed past an exposure slit 3. Through this, the exposuretime of the sensitometer A is determined."Synchronous'with the filmstripI, a density-wedge 5 is used between-the slit 3-and the light source orexposure lamp4.-Through' this density wedge 5, the radiation intensitystriking the film l is varied. Withfilms coated on two sides the lightbeam can besplitusing atwo-armed light conductor which isintroducedbehind the density wedge 5. The decisive advantage of-suchsensitometersA lies in the fact that only one narrow slit 3 must be-exposed.Therefore, low-power lamps can be used. the lamp current of which can bestabilized simply. 4

'When the filmstrip I has passed the sensitometer A'it is grasped in alongitudinal guide 6, which also can extend through thesensitometerA, bythe entrance rollers 7 of the developing-fixing-washing-drying unit Band pulled into it. The filmstrip, in its'guideway is then passed fromthe pair of entrance rollers 7 to the next pair of rollers 7', etc.,from roller pair to roller pair and by means of the guideway 6 is ledthrough the developer'tank-8, the fixing bath 9, the washing bath l0 andthe drying chamber 11. The pair of exit rollers 7" thendirects thefilmstripto the densitometer C. The velocity of the filmstrip lthroughthe developing-fixing-washing-drying unit B is constant andadjusted to the transport velocity in the sensitometer A. Within thedensitometer C the transport velocity of the filmstrip is controlled bythe densitometer C itself.

The densitometer C is a digital densitometer. It contains a measurementtransmitter=2l, a light source or exposure lamp 22, and a guideway 20for the film. In guideway 20 slit I9, illuminated by'li'ght sourceor'exposure lamp 22, is disposed opposite measurement transmitter 21;from this slit the filmstrip .is exposed fordetermination of itsdensity.

Inthe example shown, anelectronic evaluating apparatus is attached to.the densitometer C, in which the values for fog,

sensitivity and contrast are determined from the density curve thevaristor load impedance VDR, the function potentiometer 24 the parallelresistances 26 of which are indicated only by dotted lines, and thecurrent U0. In the example of FIG. 2, the balancing arrangement containsan operation amplifier 31 to compare the signal on tap 29 of thefunction potentiometer 24 with the measured signal at point 30 betweenthe photoconductive cell 21 and the varistor load impedance VDR. Twoimpulse shapers IF 1 and IF 2 are connected to the operation amplifier31. To eachof the impulse shapers IF 1 and IF 2 an AND-gate &l and &2are connected. These AND gates carry an L-signal at'their output onlywhen all inputs carry L-signals. The two AND-gates &l and &2 areattached with the second input to an impulse generator AF 1. TheAND-gate &l for the forward counting is attached with its output to theevaluating apparatus D and through an electronic switch 33 to step motorM I for the step-by-step displacement of the tap 29 of the functionpotentiometer 24. The function potentiometer 24 and the adjusting motorM I are adjusted toward one another so that each displacement stepcorresponds to th part of a density unit.

In the device represented above, the analog-digital conversion takesplace quite simply. The difference voltage at the measuring bridge isamplified with the operation amplifier 3], so that the two impulseshapers IF 1 and IF 2 conduct L- signals with an unbalanced bridge andO-signals with a balanced bridge. Through this, the AND-gates &l and &2are prepared to let L-signals through from the impulse generator AF 1.The AND-gate 81.2, provided for the backward counting and the backwarddisplacement, is switched off in such a case through a switch 34activated automatically by the sample 1 in the guideway of theapparatus. Naturally, in this way samples 1 can be measured only fromtheir least darkened side.

Therewith, a condition is achieved in which pinholes (nadelstichahnlicheklare Stellen) and fine, light scratches in the sample do not interferewith the measuring process and the measured result. Therefore, theAND-gate &2 serves essentially, with closed switch 34, that is afterremoval of the sample from the apparatus, to return the functionpotentiometer 24 to the original position. An L-signal located at theoutput of the AND-gate &1 is led to the evaluation apparatus D and thereis stored and indicated. Besides, this L-signal is fed through theelectronic switch 33 to the motor M l and there is used to displace thetap 29 in the direction of greater density. If, with the onedisplacement step, the bridge is still not balanced and, therefore,there is still an L-signal at the impulse shaper IF 1, the next L-signalfrom the impulse generator AF 1 will be let through the AND-gate &1until the bridge is balanced.

When the bridge is balanced, there is an O-signal at the output of theimpulse shaper IF 1. Through this, the AND-gates &l and &2 are closedfor the L-signals of the impulse generator AF 1. Therefore, there can beno further counting in the evaluation apparatus D and no furtherdisplacement of the function potentiometer 24 can take place. Inaddition, through the impulse inverters I l and I 2, a third AND-gate &3is attached to the impulse shapers IF 1 and IF 2 which guides theL-signals of a second impulse generator AF 2 over an electronic switch35 to the transport step motor M 2 for the sample. In this way theAND-gate &3 has the required L-signals at all inputs only when O-signalsare present at the outputs of the impulse shapers IF I and IF 2, that iswhen the bridge is balanced.

In the example of FIG. 2, in addition, a curve recorder 36 is provided,the drum of which is driven for the X-coordinate of the curves by thetransport of the sample 1 through an impulse shaper IF and an electronicswitch 37 as well as by a step motor M 3. The Y-values of the curves areformed by a potentiometer 38, the tap 39 of which, together with the tap29 of the function potentiometer 24 is driven by the step motor M l.

Consequently, the above-described apparatus gives a direct digitalmeasurement of the density and, if desired, also a continuous densitycurve.

In the embodiment according to FIG. 3 of an apparatus according to theinvention, aside from the drive for the filmstrip there are no othermechanically moving parts. Also, the counting decades in the evaluationapparatus D should be of an electronic type. The bridge system isreplaced by an electronic servosystem.

In the example of FIG. 3, a constant voltage Ue is applied to thephotoconductive cell 21, so that the current Ie flowing through thephotoconductive cell 21 is a function of the density to be measured. Anoperation amplifier 41 is connected to this photoconductive cell 21,which has a diode 42 with a logarithmic U-I curve in the feedbackbranch. In this way, the photoelectric cell 21, the operation amplifier41 and the diode 42 form a logarithmic amplifier, which already largelylinearizes the U-D curve. This logarithmic amplifier is applied to theinput of an operation amplifier 43 (which corresponds to the operationamplifier 31 in example 2). The second input of the operation amplifier43 is applied over a function generator 49 and a digital-analogconverter48 to the counter 44. Therefore, in the operation amplifier 43,the signal coming from the logarithmic amplifier 21, 41, 42 and a signalcoming from the counter 44 are compared. If the two signals are thesame, the operation amplifier 43 produces an O-signal at the output ofeach of the impulse shapers IF I and IF 2 connected on the load side ofit. If the input signals on the operation amplifier 43 are not the same,L-signals are formed at the output of the impulse shapers IF 1 and IF 2.As in example2, the L- signals appearing at the outputs of the impulseshapers IF 1 and IF 2 are led to AND-gates &] and &2 to control the L-signals of an impulse generator AF. As in example 2, the impulse shaperIF 2 and the AND-gate &2 are thought of as beingfor the resetting of theapparatus, Therefore, preferably in guideway channel, a switch Sprovided for the sample 1 is applied to the AND-gate &2, which with thesample in place continuously gives an O-signal at the input, and with anempty guideway channel gives an L-signal. Behind the voltage comparator45 formed by the operation amplifier 43 the two impulse shapers IF I andIF 2, as indicated by dotted lines, the control for the sample advance,formed as in example 2 from impulse inverters and an AND gate, can beconnected. However, since the measuring procedure and the balancing inthe apparatus according to FIG. 3 take place much faster than themechanical advance of the sample, an advance control 46 in the balancedstate of the apparatus is no longer absolutely necessary.

The final signal is conducted from AND-gate &l to the evaluationapparatus D in the forward direction to the counter 44. The counter 44again is connected to the input of a digitalanalog converter 48 whichdelivers a voltage to the function generator 49 that is proportional tothe position of the counter at the time. The function generator 49consists essentially of an operation amplifier 50 with biased diodes51a, 51b, etc., in the feedback branch. Through suitable calibration acondition can be reached in which a voltage curve dependent on the stateof the counter results at the output of the function generator 49, thatis equal to the voltage curve at the output of the logarithmic amplifier21, 41, 42 as a function of the density ahead of the photoconductivecell 21. Consequently, the comparison signals fed to the voltagecomparator 45 from the function generator 49, as in example 2, are afunction of the impulse number stored in the counter as a modifiedfunction of the characteristic of the measurement transmitter.

Iclaim:

1. Apparatus for the automatic sensitometric testing of photographicfilm, characterized by the following units in direct succession, whichare correlated with respect to the speed of transport of a photographicfilm passed through the apparatus,

A. an exposing unit having means for guiding a film to be tested, anexposure slit adjacent said guiding means, an exposure lamp behind saidslit, means to grip the film and to transport it at a constant rate ofspeed past the slit, a density wedge arranged to be moved parallel tosaid film and past said slit to vary the film exposure by varying thewedge density within a film area moved in synchronism with the wedgepast the slit;

B. a developing and fixing bath combined with washing and dryingsections for the exposed film to be tested, and

C. a densitometer having guiding means for the developed and fixed film,an exposure slit, an exposure lamp behind said slit, and a photoelectricmeasurement transmitter opposite to the said slit, said densitometerfurther having means to transport said film at a controlled rate ofspeed, and an evaluation device operatively connected to saidphotoelectric measurement transmitter to evaluate the characteristics ofthe film from the density curve measured in the film area that was movedsimultaneously with the said density wedge past the exposure slit in thesaid exposing unit.

2. Apparatus according to claim 1, characterized in that thesensitometer is provided with a two-armed light conductor for splittingthe light beam and exposing filmstrips with coatings on both surfaces.

3. In an apparatus according to claim I, an evaluation deviceconstructed to convert the output of said photoelectric measurementtransmitter into a linearized digital output to form a digitaldensitometer having linearizing arrangements.

4. In an apparatus according to claim 1, the developing and fixing bathbeing combined with the washing section and the drying section to form acomposite film testing and processing machine.

5. Apparatus according to claim 3, characterized in that a processcomputer is attached to the digital densitometer for the guidance andcontrol of the manufacturing process.

6. Apparatus according to claim 3, characterized in that the digitaldensitometer contains a balancing arrangement of the type of a bridgeconnection with a function potentiometer.

7. Apparatus according to claim 3, characterized in that the digitaldensitometer contains a balancing arrangement of the type of anelectronic servosystem with a function generator.

8. Apparatus according to claim 4, characterized in that theroll-developing machine, in addition to its transport rollers 5 containsa continuous guideway for the filmstrip, which extends from the exit ofthe sensitometer to the entrance of the densitometer.

1. Apparatus for the automatic sensitometric testing of photographic film, characterized by the following units in direct succession, which are correlated with respect to the speed of transport of a photographic film passed through the apparatus, A. an exposing unit having means for guiding a film to be tested, an exposure slit adjacent said guiding means, an exposure lamp behind said slit, means to grip the film and to transport it at a constant rate of speed past the slit, a density wedge arranged to be moved parallel to said film and past said slit to vary the film exposure by varying the wedge density within a film area moved in synchronism with the wedge past the slit; B. a developing and fixing bath combined with washing and drying sections for the exposed film to be tested, and C. a densitometer having guiding means for the developed and fixed film, an exposure slit, an exposure lamp behind said slit, and a photoelectric measurement transmitter opposite to the said slit, said densitometer further having means to transport said film at a controlled rate of speed, and an evaluation device operatively connected to said photoelectric measurement transmitter to evaluate the characteristics of the film from the density curve measured in the film area that was moved simultaneously with the said density wedge past the exposure slit in the said exposing unit.
 2. Apparatus according to claim 1, characterized in that the sensitometer is provided with a two-armed light conductor for splitting the light beam and exposing filmstrips with coatings on both surfaces.
 3. In an apparatus according to claim 1, an evaluation device constructed to convert the output of said photoelectric measurement transmitter into a linearized digital output to form a digital densitometer having linearizing arrangements.
 4. In an apparatus according to claim 1, the developing and fixing bath being combined with the washing section and the drying section to form a composite film testing and processing machine.
 5. Apparatus according to claim 3, characterized in that a process computer is attached to the digital densitometer for the guidance and control of the manufacturing process.
 6. Apparatus according to claim 3, characterized in that the digital densitometer contains a balancing arrangement of the type of a bridge connection with a function potentiometer.
 7. Apparatus according to claim 3, characterized in that the digital densitometer contains a balancing arrangement of the type of an electronic servosystem with a function generator.
 8. Apparatus according to claim 4, characterized in that the roll-developing machine, in addition to its transport rollers contains a continuous guideway for the filmstrip, which extends from the exit of the sensitometer to the entrance of the densitometer. 